1. Field of the Invention
This invention relates to an apparatus for conducting plasma separation/exchange by double filtration in a safe and steady manner.
2. Description of the Prior Art
Plasma separation and exchange is a recently developed therapy for renal failure, hepatic failure, autoimmune diseases and so on. This technique, like blood dialysis, generally comprises separating plasma continuously in a closed extracorporeal circuit and returning a plasma fraction to the body of the patient. Another plasma fraction, which is discarded, contains low-molecular-weight active components bound to high-molecular-weight toxins or the like, and removal of these necessitates a correspondingly larger amount of substitute fluid. Therefore, various attempts have so far been made to remove such high-molecular-weight substances in an efficient manner. Among others, plasma separation and exchange is noteworthy. This technique uses two filter means which are different in their low-molecular-weight substance cut-off performance. The first filter means performs separation into a plasma fraction and a corpuscular fraction, and the second filter means separates the plasma fraction into a high-molecular-weight fraction and a low-molecular-weight fraction. The high-molecular-weight fraction alone is selectively removed and the low-molecular-weight-fraction is returned to the body.
Pioneer studies of the specific plasma component permeation method have already been made and described. For example, there is a report by T. Agishi et al, published in the Japanese Journal of Medical Instrumentation, vol. 49, Supplement, p. 259-261 (1979). Also, a Japanese patent application laid open under No. 2444/1980 discloses a blood treatment apparatus in which a specific plasma component permeation method is realized in combination with a water-removing means.
However, these techniques known in the art, though called techniques, are no more than proposals of possibilities or theoretical apparatus. No disclosure is contained therein for an actual apparatus useful in medical practice.